An ion trap mass spectrometer configured for on-line HPLC fractionation and atmospheric pressure ionization is needed to support ongoing research activities of an interdisciplinary group of investigators at the University of Texas Health Science Center at San Antonio. The instrument requested, a Finnigan MAT LCQ will become a part of the institutional Mass Spectrometry Laboratory, under the direction of Dr. Susan Weintraub Research in progress at this health science center will profit substantially by the instrument's abilities to provide peptide and protein characterization and sequencing, structural elucidation of endogenous ant xenobiotic metabolites and identification/verification of synthetic candidate chemotherapeutic agents. These studies cannot otherwise be accomplished, due to limitations in the laboratory current instrumentation. Acquisition of the LCQ will yield the added benefit of permitting reorganization of this laboratory so that the Finnigan MAT SSQ700 which is currently being employed for peptide/protein analyses can assume the GC/MS responsibilities of a heavily utilized obsolete mass spectrometer. The positive effects of expanding the Mass Spectrometry Laboratory's capabilities to include on-line HPLC fractionation with tandem mass spectrometry will impact a great number of researchers across varied disciplines of biomedical research.